Topological optimization method for body skeleton of electric vehicle

Abstract

The invention relates to the technical field of automobile design, and discloses an electric automobile body skeleton topological optimization method which comprises the following steps that an initial body skeleton model of an electric automobile is obtained, and the model comprises main structural components and connection relations of an automobile body; determining design variables of the vehicle body framework, wherein the design variables comprise the material type and thickness distribution of the vehicle body framework; based on a topological optimization algorithm, performing optimization calculation on the initial vehicle body skeleton model to generate a plurality of optimization schemes, the optimization calculation adopting a multi-objective optimization strategy; and screening and evaluating the generated optimization schemes, and selecting the optimization scheme meeting a predetermined performance index. A topological optimization algorithm is adopted to carry out global optimization design on a vehicle body framework, and material distribution is dynamically adjusted in a design area, so that optimization of structural performance is realized. A multi-objective optimization strategy is adopted in the optimization calculation process, so that the light weight and the rigidity of the vehicle body framework are optimized at the same time.

Description

Technical Field

[0001] This invention relates to the field of automotive design technology, specifically to a method for optimizing the topology of an electric vehicle body frame. Background Technology

[0002] With the increasing severity of the global energy crisis and environmental pollution, electric vehicles, as a clean energy mode of transportation, have received widespread attention and rapid development. The body frame design of electric vehicles plays a crucial role in their overall performance, directly affecting vehicle safety, comfort, and energy efficiency.

[0003] Traditional vehicle body frame design methods have many shortcomings and cannot simultaneously meet the requirements of lightweighting and high performance. Traditional vehicle frame design relies heavily on engineers' experience and experimental data, involving repeated trials and adjustments to determine the final design. This method is not only time-consuming and labor-intensive but also struggles to guarantee the overall optimality of the design, as it typically fails to adequately consider the stress conditions of the vehicle frame under different operating conditions, potentially leading to performance deficiencies in certain scenarios. While finite element analysis (FEM) is widely used in vehicle frame design to evaluate structural performance through static and dynamic load analysis, it is primarily used for design verification and optimization, making it difficult to provide global optimization guidance in the early stages of design. Furthermore, traditional FEM methods are usually based on pre-defined geometries and material distributions, hindering the dynamic adjustment and optimization of the vehicle frame's structural form and material distribution during the design process. Lightweight vehicle frame design is a crucial direction for electric vehicle development. Reducing the mass of the vehicle frame can effectively improve energy efficiency and driving range. However, lightweight design requires minimizing material usage while maintaining structural performance, placing higher demands on design methods. Existing lightweight design methods often struggle to simultaneously meet performance requirements in multiple aspects, such as stiffness, strength, and collision safety, resulting in deficiencies in certain performance indicators. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a topology optimization method for electric vehicle body frames. This method uses a topology optimization algorithm to perform global optimization design on the body frame, thereby achieving the goals of lightweighting and high performance.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for topology optimization of an electric vehicle body frame, comprising the following steps:

[0006] Obtain an initial body frame model of the electric vehicle, the initial body frame model including the main structural components of the body and their connection relationships;

[0007] Determine the design variables for the vehicle body frame, including the material type and thickness distribution of the vehicle body frame;

[0008] Based on the topology optimization algorithm, the initial vehicle body frame model is optimized to generate multiple optimization schemes, wherein the optimization calculation adopts a multi-objective optimization strategy.

[0009] The generated optimization schemes are screened and evaluated, and the optimization schemes that meet the predetermined performance indicators are selected.

[0010] The selected optimization scheme was designed and experimentally verified in detail, including fine-tuning the geometry and material distribution of the vehicle body frame. The experimental verification used the finite element analysis method to verify the structural performance of the optimization scheme under static and dynamic load conditions.

[0011] Based on the experimental verification results, the optimization scheme was adjusted and improved, and iterative optimization was carried out until all predetermined performance indicators were met.

[0012] The final vehicle body frame design will be applied to the manufacturing and assembly process of electric vehicles to ensure the feasibility and economy of the design and optimize manufacturing processes and assembly procedures.

[0013] Preferably, the material types of the vehicle body frame include aluminum alloy, steel and composite materials, and the thickness distribution is optimized according to different parts of the vehicle body frame and the stress conditions, so as to meet the structural performance requirements and achieve the optimal allocation and use of materials.

[0014] Preferably, the multi-objective optimization strategy is to simultaneously optimize the lightweighting and stiffness of the vehicle body frame. By setting weight coefficients, the relationship between lightweighting and stiffness is balanced so that the optimization result meets the lightweighting requirements while having sufficient structural stiffness.

[0015] Preferably, the screening and evaluation steps include a comprehensive evaluation of the structural performance and manufacturing cost of the optimized scheme. The structural performance evaluation includes static strength, dynamic stiffness and vibration modal analysis, and the manufacturing cost evaluation includes material cost, processing cost and assembly cost.

[0016] Preferably, the static load analysis includes static strength and stiffness analysis, and the dynamic load analysis includes vibration mode and fatigue life analysis, to ensure the structural performance of the optimized scheme under various working conditions.

[0017] Preferably, the experimental verification step includes manufacturing and testing a physical prototype of the optimized scheme. The physical prototype testing includes static strength testing, dynamic vibration testing, and collision safety testing. The actual performance of the optimized scheme is verified through experimental data, and necessary adjustments and improvements are made based on the test results.

[0018] Preferably, the iterative optimization process includes redefining the design variables and the parameters of the topology optimization algorithm, performing multiple optimization calculations and evaluations to ensure the optimality and feasibility of the final design scheme.

[0019] Preferably, the topology optimization algorithm employs a density method, which optimizes structural performance by allocating different material densities within the design region.

[0020] Preferably, the topology optimization algorithm employs the level set method, which optimizes structural performance by tracking interface changes within the design region.

[0021] Preferably, the topology optimization algorithm employs an evolutionary structural optimization method, which optimizes structural performance by gradually removing or adding materials.

[0022] This invention provides a method for topology optimization of an electric vehicle body frame. It has the following beneficial effects:

[0023] This invention employs a topology optimization algorithm for global optimization design of the vehicle body frame, achieving optimal structural performance by dynamically adjusting material distribution within the design region. A multi-objective optimization strategy is used during the optimization calculation process to simultaneously optimize both lightweighting and stiffness of the vehicle body frame. By setting weighting coefficients, the relationship between lightweighting and stiffness is balanced, ensuring that the optimization result meets lightweighting requirements while possessing sufficient structural stiffness. The generated optimization scheme is comprehensively evaluated, including structural performance, manufacturing cost, and feasibility. Finite element analysis and experimental verification are used to conduct detailed design and verification of the optimization scheme, and iterative optimization is performed based on the verification results until all predetermined performance indicators are met. The final design scheme can be directly applied to the manufacturing and assembly process of electric vehicles. By optimizing manufacturing processes and assembly procedures, the feasibility and economy of the design scheme are ensured, improving the overall performance and market competitiveness of electric vehicles. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the steps of a method for topology optimization of an electric vehicle body frame according to the present invention;

[0025] Figure 2 This is a schematic diagram of the density method steps in this invention;

[0026] Figure 3 This is a schematic diagram illustrating the steps of the level set method in this invention;

[0027] Figure 4 This is a schematic diagram illustrating the steps of the evolutionary structure optimization method in this invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] Please see the appendix Figure 1 Appendix Figure 2 This invention provides a method for topology optimization of an electric vehicle body frame, which uses the density method for topology optimization calculation, and includes the following steps:

[0031] Step 1: Obtain the initial body frame model of the electric vehicle. The model includes the main structural components of the body, such as the front and rear frames, side beams, cross beams, etc., as well as the connection relationships between the various components.

[0032] The design variables and constraints of the vehicle body frame are determined, including but not limited to material properties, geometric dimensions, load conditions, and boundary conditions. The design variables include the material type and thickness distribution of the vehicle body frame. The material type may include, but is not limited to, aluminum alloys, steel, and composite materials. The thickness distribution is optimized according to different parts of the vehicle body frame and the stress conditions to ensure that the optimal allocation and use of materials are achieved while meeting the structural performance requirements. The constraints include the maximum stress and maximum deformation of the vehicle body frame. The maximum stress shall not exceed the yield strength of the material, and the maximum deformation shall not exceed the design allowable value to ensure the safety and reliability of the vehicle body frame under various working conditions.

[0033] Step 2: Based on the density method topology optimization algorithm, optimize the initial car body frame model and generate multiple optimization schemes. The optimization calculation process considers the performance indicators of the car body frame such as lightweighting, stiffness and strength. That is, the optimization calculation adopts a multi-objective optimization strategy, and simultaneously optimizes the lightweighting and stiffness of the car body frame. By setting the weight coefficients, the relationship between lightweighting and stiffness is balanced so that the optimization results meet the lightweighting requirements while having sufficient structural stiffness.

[0034] The specific optimization calculation process using the density-based topology optimization algorithm is as follows:

[0035] S1. Initial Model Establishment

[0036] Based on the initial body skeleton model of the electric vehicle obtained in step one, the software is used to establish the initial design domain, define the geometry and mesh division of the design domain, and set the material properties.

[0037] Define the boundary conditions of its structure, such as fixed ends and free ends;

[0038] Apply external loads, such as concentrated and distributed forces;

[0039] S2. Define design variables and set objective function and constraints.

[0040] The design variable is typically the density value of each finite element, denoted as p. i , where 0≤p i ≤1. p i =1 indicates that the cell is filled with material, p i =0 indicates that the cell is empty, and the design variable p is usually defined. i The initial value is 0.5;

[0041] The objective function, typically minimizing the flexibility of the structure (i.e. maximizing its stiffness), can be expressed as:

[0042]

[0043] Where f is the external load vector, u is the displacement vector, and K(p) is the stiffness matrix of the structure;

[0044] Constraints, specifically volume constraints, which limit the total amount of material used, can be expressed as:

[0045]

[0046] Among them, V i V is the volume of the i-th unit. max This is the maximum allowed volume;

[0047] The stiffness matrix K(p) is interpolated using the SIMP method:

[0048]

[0049] Among them, K i is the stiffness matrix of the i-th element, and q is the penalty factor, which is usually 3.

[0050] S3, Finite Element Analysis

[0051] Based on the current design variable p i Calculate the stiffness matrix K(p) of the structure and perform finite element analysis to solve for the displacement vector u;

[0052] S4, Sensitivity Analysis

[0053] Calculate the sensitivity of the objective function to the design variables, i.e. The results of its sensitivity analysis are used to guide the updating of design variables;

[0054] S5. Updating Design Variables

[0055] Based on the results of the sensitivity analysis, the gradient descent method is used to update the design variable x. The update formula is:

[0056]

[0057] Where α is the step size factor;

[0058] S6, Filtering and Projection

[0059] To avoid numerical instability and grid dependency, design variables are typically filtered and projected. Filtering can be achieved using the Helmholtz equations:

[0060]

[0061] in, This is the density value after filtration, w ij It is the weight function, and N(i) is the neighborhood of the i-th unit;

[0062] S7, Iterative Optimization

[0063] Repeat steps S3 to S6 until the objective function converges or the predetermined number of optimizations is reached.

[0064] Step 3: Screen and evaluate the generated optimization schemes, and select the optimization schemes that meet the predetermined performance indicators. The screening and evaluation steps include a comprehensive evaluation of the structural performance and manufacturing cost of the optimization schemes. The structural performance evaluation includes static strength, dynamic stiffness and vibration mode analysis, and the manufacturing cost evaluation includes material cost, processing cost and assembly cost.

[0065] Step 4: Conduct detailed design and experimental verification of the selected optimization scheme, including fine adjustment of the geometry and material distribution of the vehicle body frame, and use the finite element analysis method to verify the structural performance of the optimization scheme under static and dynamic load conditions. Static load analysis includes static strength and stiffness analysis, and dynamic load analysis includes vibration mode and fatigue life analysis, to ensure the structural performance of the optimization scheme under various working conditions.

[0066] Step 5: Based on the experimental verification results, adjust and improve the optimization scheme, and perform iterative optimization until all predetermined performance indicators are met. The iterative optimization process includes redefining the design variables and the parameters of the topology optimization algorithm, performing multiple optimization calculations and evaluations to ensure the optimality and feasibility of the final design scheme. The experimental verification step includes manufacturing and testing a physical prototype of the optimization scheme. The physical prototype test includes static strength test, dynamic vibration test and collision safety test. The actual performance of the optimization scheme is verified through experimental data, and necessary adjustments and improvements are made based on the test results.

[0067] The final vehicle body frame design will be applied to the manufacturing and assembly process of electric vehicles to ensure the feasibility and economy of the design and optimize manufacturing processes and assembly procedures.

[0068] Example 2:

[0069] Please see the appendix Figure 1 Appendix Figure 3 This invention provides another method for topology optimization of electric vehicle body frames. Unlike the above embodiments, it uses the level set method for topology optimization calculation, mainly optimizing structural performance by tracking interface changes within the design region. The relevant calculation formulas are as follows:

[0070] The optimization calculation process is as follows:

[0071] Level set function Indicates the boundary. Indicates the material area. Indicates an empty region.

[0072] Level set equation

[0073] The evolution of the level set function is described by the following partial differential equation:

[0074]

[0075] Where F is the velocity function, It is the gradient of the level set function;

[0076] The velocity function F is typically related to the structure's geometric properties (such as curvature) and physical properties (such as stress). A common choice is a velocity function based on curvature:

[0077] F = -k

[0078] Where k is the curvature;

[0079] The curvature k can be calculated using the gradient of the level set function and the Laplace operator:

[0080]

[0081] The specific optimization process includes the following steps:

[0082] A1. Initial Model Establishment

[0083] Based on the initial body skeleton model of the electric vehicle, the initial design domain is established using software, the geometry and mesh division of the design domain are defined, and the material properties are set.

[0084] Define the boundary conditions of its structure, such as fixed ends and free ends;

[0085] Apply external loads, such as concentrated and distributed forces;

[0086] A2. Initialization of level set functions

[0087] Define the level set function based on the geometry of the initial design domain. Typically, the initial level set function can be a distance function.

[0088] A3. Finite Element Analysis

[0089] Based on the current level set function Calculate the stiffness matrix K of the structure and perform finite element analysis to solve for the displacement vector u;

[0090] The structure is divided into finite element meshes, and the nodes of each element are used to calculate the stiffness matrix K(p), where K(p) = ∫B T DBdVe, where B is the strain-displacement matrix, D is the material elasticity matrix, and Ve is the element volume, and the stiffness matrix K(p) of all elements is assembled into the global stiffness matrix K.

[0091] Based on the current level set function Perform finite element analysis to calculate the stress and strain distribution of the structure;

[0092] By solving the linear equation system K u =f, where u is the displacement vector and f is the external force vector. The strain of each element is calculated using the displacement vector u: ε = Bu; then the stress is calculated using the material's elastic matrix D: σ = Dε;

[0093] A4. Sensitivity Analysis

[0094] Calculate the sensitivity of the objective function (such as structural flexibility or stress), that is, the derivative of the objective function with respect to the design variables;

[0095] Based on the results of the sensitivity analysis, a velocity field F is constructed to drive the evolution of the level set.

[0096] A5. Level Set Function Update

[0097] Solve the level set equation using either explicit or implicit difference methods, and update the level set function. Meanwhile, to maintain the numerical stability of the level set function, it is periodically reinitialized, so that... Preserve it in the form of a distance function;

[0098] A6. Iterative Optimization

[0099] Repeat steps A3 to A5 until the objective function converges or the predetermined number of optimization iterations is reached.

[0100] Example 3:

[0101] Please see the appendix Figure 1 Appendix Figure 4 This invention provides another method for topology optimization of electric vehicle body frames. Unlike the above embodiments, it uses an evolutionary structural optimization method for topology optimization calculations. It mainly optimizes structural performance by tracking interface changes within the design region. The relevant calculation formulas are as follows:

[0102] Design variables are typically the state of existence of each finite element, denoted as p. i , where p i =1 indicates that the cell exists, and ρi=0 indicates that the cell has been removed;

[0103] The objective function, typically minimizing the flexibility of the structure (i.e. maximizing its stiffness), can be expressed as:

[0104]

[0105] Where f is the external load vector, u is the displacement vector, and K(p) is the stiffness matrix of the structure;

[0106] Evolutionary structure optimization methods remove or add materials based on stress criteria. The stress criterion can be expressed as: σ i ≤σ crit

[0107] Where, σ i It is the stress of the i-th element, σ crit It is the critical stress value;

[0108] The optimization calculation process steps are as follows:

[0109] T1. Establish the initial design domain and define the design variable p. i The initial value is set (usually 1), and the objective function and constraints are set;

[0110] T2, based on the current design variable p i Calculate the stiffness matrix K(p) of the structure and perform finite element analysis to solve for the displacement vector u;

[0111] T3. Calculate the stress σ of each element. i and with the critical stress value σ crit Compare;

[0112] T4, Material Removal

[0113] Remove stress below the critical stress value σ crit The unit, i.e., setting σ i =0, which can be achieved through the following criteria:

[0114]

[0115] T5. Material Addition (Optional)

[0116] In some cases, material can be added in areas where the stress is above the critical stress value, i.e., σ can be set. i =1,

[0117] This can be achieved through the following criteria:

[0118]

[0119] T6. Repeat steps T2 to T5 until the objective function converges or the predetermined number of optimization iterations is reached. After each iteration, update the design variable p. i And recalculate the stiffness matrix and stress distribution of the structure.

[0120] Based on the three embodiments described above, a two-dimensional cantilever beam is optimized. The initial design domain is rectangular, and the boundary conditions are a fixed left end and a downward concentrated force applied to the right end. Through evolutionary structural optimization, elements with low stress are gradually removed, ultimately resulting in an optimized cantilever beam structure. The material is mainly concentrated in the area with higher stress, forming a truss-like structural form.

[0121] The optimization results are shown in the table below:

[0122]

[0123] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for topology optimization of an electric vehicle body frame, characterized by, The method includes the following steps: Obtain an initial body frame model of the electric vehicle, the initial body frame model including the main structural components of the body and their connection relationships; Determine the design variables for the vehicle body frame, including the material type and thickness distribution of the vehicle body frame; Based on the topology optimization algorithm, the initial vehicle body frame model is optimized to generate multiple optimization schemes, wherein the optimization calculation adopts a multi-objective optimization strategy. The generated optimization schemes are screened and evaluated, and the optimization schemes that meet the predetermined performance indicators are selected. The selected optimization scheme was designed and experimentally verified in detail, including fine-tuning the geometry and material distribution of the vehicle body frame. The experimental verification used the finite element analysis method to verify the structural performance of the optimization scheme under static and dynamic load conditions. Based on the experimental verification results, the optimization scheme was adjusted and improved, and iterative optimization was carried out until all predetermined performance indicators were met. The final vehicle body frame design will be applied to the manufacturing and assembly process of electric vehicles to ensure the feasibility and economy of the design and optimize manufacturing processes and assembly procedures.

2. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The materials used in the vehicle frame include aluminum alloy, steel, and composite materials. The thickness distribution is optimized according to different parts of the vehicle frame and the stress conditions to meet structural performance requirements and achieve optimal material allocation and use.

3. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The multi-objective optimization strategy simultaneously optimizes the lightweighting and stiffness of the vehicle body frame. By setting weight coefficients, the relationship between lightweighting and stiffness is balanced, so that the optimization result meets the lightweighting requirements while having sufficient structural stiffness.

4. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The screening and evaluation steps include a comprehensive evaluation of the structural performance and manufacturing cost of the optimized scheme. The structural performance evaluation includes static strength, dynamic stiffness and vibration modal analysis, and the manufacturing cost evaluation includes material cost, processing cost and assembly cost.

5. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The static load analysis includes static strength and stiffness analysis, while the dynamic load analysis includes vibration mode and fatigue life analysis, to ensure the structural performance of the optimized scheme under various working conditions.

6. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The experimental verification steps include manufacturing and testing a physical prototype of the optimized scheme. The physical prototype testing includes static strength testing, dynamic vibration testing, and collision safety testing. The actual performance of the optimized scheme is verified through experimental data, and necessary adjustments and improvements are made based on the test results.

7. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The iterative optimization process includes redefining the design variables and the parameters of the topology optimization algorithm, performing multiple optimization calculations and evaluations to ensure the optimality and feasibility of the final design scheme.

8. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The topology optimization algorithm employs a density method, which optimizes structural performance by allocating different material densities within the design region.

9. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The topology optimization algorithm employs the level set method, which optimizes structural performance by tracking interface changes within the design region.

10. The electric vehicle body frame topology optimization method according to claim 1, characterized in that, The topology optimization algorithm employs an evolutionary structural optimization method, which optimizes structural performance by gradually removing or adding materials.

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